In an OTN (Optical Transport Network), which is a high-capacity broad area optical transport network, transfer is performed by accommodating a client signal by various standards, such as SDH (Synchronous Digital Hierarchy) or Ethernet (registered trademark). In recent years, there has been a marked increase in client signal traffic, and an accompanying standardization of OTNs to handle higher speeds has been advanced (for example, refer to Non-Patent Document 1). Further, an OTUCn (Optical channel Transport Unit-Cn, where Cn represents 100G×n), which is an OTN technique exceeding 100G (B100G, where G represents gigabits per second), is currently being investigated (for example, refer to Non-Patent Document 2). In an OTUCn, the transmission capacity of a single optical channel becomes more broadband than a conventional OTU. However, for reasons related to the operation speed of the electronic circuits used in optical signal transceivers, it is difficult to achieve a higher capacity by expanding single carrier transmission with respect to the band of a single optical channel in a conventional manner. Therefore, in an OTUCn, a higher capacity is realized by multicarrier transmission using a plurality of optical subcarriers in the band of a single optical channel.